Pushbutton-controlled overload circuit breaker



June 6, 1967 J. ELLENBERGER 3,32

PUSHBUTTON'CONTROIJLED OVERLOAD CIRCUIT BREAKER 2 Shets-Sheet 1 1 FiledOct. 22 1965 INVENTOR.

June 6, 1967 J. ELLENBERGER PUSHBUTTON-CONTROLLED OVERLOAD CIRCUITBREAKER 2 Sheets-Sheet 2 Filed Oct. 22, 1965 INVENTOR:

United States Patent 3,324,429 FUSHBUTTON-CONTROLLED OVERLOAD CIRCUITBREAKER Jakob Ellenherger, Altdorf, near Nurnberg, Germany, as-

signor to Firma Ellenherger & Poensgen G.m.b.H.,

Altdorf, near Nnrnberg, Germany, a German firm Fiied Oct. 22, 1965, Ser.No. 500,720 Claims priority, application Germany, June 2, 1965, E 29,44112 Claims. (Cl. 335-35) The present invention relates to apushbutton-controlled overload circuit breaker which is provided with athermal release and/ or an electromagnetic release and also with atrip-free release, and further with a contact bridge. When thepushbutton of this circuit breaker is being depressed and a control rodwhich is rigidly secured to the pushbutton is moved accordingly, acarrier member on the control rod moves the contact bridge to the onposition in which the carrier member is disconnected from the contactbridge. In my previous Patent No. 2,895,028, I have described andclaimed an overload circuit breaker of the above-mentioned type which isdesigned so as to have very small outer dimensions, may be switched onand off instantaneously, and may in addition be switched oif by hand bymeans of an additional release button. The contact bridge of thiscircuit breaker is slidable as well as pivotable on the control rodwhich is rigidly secured to the pushbutton and consists of insulatingmaterial, and the trip-free release is effected by a compression springwhich is mounted on the control rod between the contact bridge and thecarrier member.

In actual practice it has been found that this overload circuit breakerhas the disadvantage that, if an additional pressure is exerted upon thepushbutton when it is already depressed and the contact bridge is in itson position in which the contact pressure is produced by the cut-offspring which acts upon the pushbutton, this spring is compressed andthereby rendered-ineffective. Therefore, when the pushbutton is in thisdepressed position, the contact pressure is produced merely by the otherspring which is adapted to effect the trip-free release of the circuitbreaker. The carrier member on the control rod which is acted upon bythis trip-free release spring is then likewise moved so that this springis released to a certain extent and the contact pressure is therebyfurther reduced. The result of such a low contact pressure may be,especially if the circuit breaker is employed for currents of a highamperage, that the resistance between the contact bridge and theassociated fixed contacts might increase so highly that these parts maybe heated to such high temperatures that they might be scorched orfreeze together."

It is an object of the present-invention to provide an overload circuitbreaker-which is of the same type as, and possesses all of theadvantages of the circuit breaker as described above and disclosed indetail in my previous Patent No. 2,895,028, but which improves thisknown circuit breaker by designing it so as to insure that, when thepushbutton is already depressed and the contact bridge is in its onposition, the contact pressure will not be changed when an additionalpressure is exerted upon the pushbutton. The overload circuit breakeraccording to the invention may therefore be employed especially forcurrents of high amperages. Another object of the invention is to designsuch an overload circuit breaker so as to have very small outerdimensions even though it is intended for high amperages, and to be of asimple construction which may be easily manufactured and assembled. Afurther object is to design the circuit breaker so that it may also beswitched off by hand.

One important feature of the invention consists in mounting the contactbridge on a pivotable control level,

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the pivot pin of which is slidable within the walls of the housing andadapted to be locked in a fixed position by a pivotable pawl when thecontact bridge is in its on position. When this pawl is in its lockingposition, it is braced on a release lever which may be pivoted to aninoperative position when an excess current occurs. The control leverwhich is connected to the contact bridge is provided with a stopprojection which, when the contact bridge is in its off position, islocated within the area of motion of a carrier member which is mountedon the control rod which, in turn, is secured to the pushbutton. Whenthe contact bridge is in its on position, this stop projection on thecontrol lever is moved out of the area of motion of the carrier member.The control lever is acted upon by a compression spring which, when thepivot pin of the control lever is locked by the pawl in a fixedposition, produces the necessary contact pressure of the contact bridgeand, when the pivot pin of the control lever is released by the pawl,moves the control lever together with the contact bridge to the olfposition.

When the contact bridge is in the on position, the control lever istherefore located in a position in which its stop projection is outsideof the area of motion of the carrier member on the control rod which isrigidly secured to the pushbutton. Therefore, if a further pressure isthen exerted upon the pushbutton when the contact bridge is already inits on position, it will have no effect upon the control lever and thusalso not upon the contact bridge and the contact pressure which isproduced by the compression spring which acts upon the control lever. Achange in the strength of the contact pressure which could occur in myprevious circuit breaker as above referred to when the pushbutton wasagain depressed 'when the circuit breaker was already switched on cantherefore not occur in the circuit breaker according to the presentinvention. The compression spring which acts upon the control leverproduces a contact pressure of a high constant strength. so that thecontact-resistance between the contact bridge and the fixed contacts isvery small and any excessive heating of the contacts is prevented andthe contacts are therefore prevented from scorching and fusing togetherso that the entire circuit breaker will therefore be properly operativefor a very long time. Since the control lever and thus the contactbridge cannot possibly be affected by the pushbutton or the carriermember when the contact bridge is in its on position, a trip-freerelease will be attained when the control lever is released by the pawlunder the action of the compression spring which acts upon the controllever. Only relatively small forces are required to move the releaselever to the position in which the pawl will no longer be supportedthereon so that a trip-free release will then occur. These releasingforces may be so small because the pawl is merely braced on the releaselever, preferably in a position vertical to the pivot axis of therelease lever.

The above-mentioned as well as further objects, features, and advantagesof the present invention will be come more clearly apparent from thefollowing detailed description thereof, particularly when read withreference to the accompanying drawings, in which FIGURE 1 shows, partlyin section, a side view of the circuit breaker according to theinvention in the on position and with one part of the housing removed;

' FIGURE 2 shows a detailed view of the pushbutton together with thecontrol rod and the carrier member according to FIGURE 1;

FIGURE 3 shows a view of the same element as in FIGURE 2, but as seenfrom the left side thereof;

FIGURE 4 shows a view similar to FIGURE 1, but with the circuit breakerin the off position;

FIGURE 5 shows a view as seen in the direction of the arrow V in FIGURE4;

FIGURE 6 shows a cross section which is taken in the directionperpendicular to the axis of the control lever, as seen from the left ofFIGURE 4; while FIGURE 7 shows a perspective view of the right upperpart of the circuit breaker according to FIGURE 4.

As illustrated in the drawings, the overload circuit breaker accordingto the invention comprises a housing of insulating material whichconsists of two separate parts, namely, the part 1 into which the switchelements are inserted and another similar part, not shown, which issecured to and covers the part 1. Both parts of the housing are providedwith recesses in which the various switch elements are held in theirproper positions relative to each other, and both parts are secured toeach other by rivets, preferably tubular rivets, which are inserted intocorresponding bores 2 in both parts of the housing.

For connecting it to an electric circuit, the circuit breaker isprovided with two terminal strips 3 and 4 and terminal screws 5 thereon.The inner end of terminal strip 3 carries a fixed contact 6 which isoperatively associated with a contact 7 on a contact bridge 8. Thiscontact bridge 8 has another contact 9 which, when the contact bridge isin its on position, as illustrated in FIG- URE 1, engages upon a fixedcontact 10 on a connecting bar 11 which is secured by a screw 12 to thehousing part 1. This connecting bar 11 is bent three times at rightangles and it is centrally slotted so that its front and rear parts areconnected at their upper ends and together form a coil winding. Arm 13of this bar 11, which, according to FIGURE 1, forms the front endthereof, is connected by a screw 14 to a part 15 which is electricallyconnected to the rear arm of the bimetal strip 16 which is likewisecentrally slotted. The front arm of the slotted bimetal strip 16 issoldered or welded at 17 to one arm 4 of the slotted terminal strip 4,the other arm 4" of which is bent toward the right and secured by ascrew 18 to the housing part 1. The slotted bar 11 and the slottedbimetal strip 16 form two coil windings through which the arm 20 of amagnet core 19 extends. This core 19 has another arm 21 which isprovided withan extension 22 which projects at a right angle from thearm 21 and extends across the entire width of bar 11 above the upper endthereof.

As shown in FIGURE 1, the left end of arm 20 of the magnet core 19 hasan upwardly bent extension 23. The magnetic circuit of core 19 may beclosed almost entirely at the extensions 22 and 23 by an armature 24which forms an arm of a release lever 26 which is pivotably mounted on apin 25. This release lever 26 has another arm 27 into which there isscrewed a setscrew 28 which has a small knob 29 of insulating materialwhich is acted upon by the bimetal strip 16 when the latter is benttoward the right from its position as shown in FIGURE 1. As illustratedparticularly in FIGURE 7, the rear arm 30 of the release lever 26 has ashoulder 31 upon which an arm 33 of a pawl 32 engages when this pawl isin its locking position, as shown in FIGURE 1. Pin 25 on which therelease lever 26 is mounted carries a torsion spring'34, one arm 35 ofwhich acts at 36 upon the pawl 32, while the other spring arm 37 actsupon the release lever 26. This'torsion spring 34 tends to maintain thepawl 32 and the release lever 26 in the positions as shown in FIGURE 1.As illustrated particularly in FIG- URE 6, pawl 32 is pivotably mountedon two rivets 38 at the inside of a metal frame 39 which is insertedinto recesses of a corresponding shape in the two parts of the housing.

FIGURE 6 further indicates that the metal frame 39 and pawl 32 areU-shaped. The two lateral parts of pawl 32 are provided withcorresponding recesses 40 forming equal detents 41 and with guide edges42 above these recesses and equal noselike projections 43 below them.Recesses 40 are adapted to receives a pivot pin 44 for a control lever45 which has likewise a U-shaped cross section. This control lever 45has an upper arm 46 which is acted upon by a compression spring 47, thelower end of which rests upon the. bottom 48 of a recess 49 in thehousing part 1. The ends of pivot pin 44 are slidable and guided withinslots 50 in the metal frame 39, as may be seen particularly in FIGURE 6.The two lateral parts of control lever 45 have corresponding bores inwhich short pivot pins 51 on a one-armed lever 52 are pivotable. Lever52, in turn, is pivotably connected by a pin 53 to the contact bridge 8.As illustrated in FIGURE 1, contact bridge 8 is stamped so as to form acentral rectangular or L-shaped part 54 which carries the contacts 7 and9, and front and rear parts 54' which are partly separated by slots fromthe central part 54 and are bent in the direction opposite to thecentral part so that all three parts together form a bearing into whichthe pivot pin 53 may be inserted. As may be seen in FIGURE 4, theopposite ends of pin 53 are slidable in corresponding grooves 55 in thetwo housing parts. The two lateral parts of control lever 45 areprovided with notches 56 constituting stop projections into which a pairof small lateral projections 58 on a carrier member 57 may engage duringthe downward movement of the latter when the switch mechanism is in itsoff position as illustrated in FIGURE 4. As shown in FIGURE 2, thecarrier member 57 is pivotably mounted by pivot pins 59 on a part 60which is rigidly secured to the lower end of the control rod 62, and itis acted upon by a small compression spring 61 which tends to maintainit in the position as shown in full lines in FIGURE 2. The two sides ofpart 60 carry projections 60' which are slidable i-n correspondinggrooves 62' in the two parts of the housing so as to guide the controlrod 62. The upper end of the control rod 62 is rigidly secured to apushbutton 63 which is guided within an externally threaded bushing 64and is acted upon by a cut-off spring 65 which is wound around thecontrol rod 62 and the lower end of which rests on an insulating washer66 which is held on an inner flange 67 of the housing part 1.

Bushing 64 carries a nut 68 and a curved spring washer 69, and its lowerend is riveted to a metal plate 70. As shown in FIGURE 3, the outer endsof this plate 70 are provided with T-shaped projections 71 which, wheninserted into corresponding recesses in the right upper edges of bothparts of the housing as indicated in FIG- URE 7, secure this metal plate70 rigidly to the housing when the two parts thereof are secured to eachother. Plate 70 is preferably separated from the upper side of the twohousing parts by an insulating strip 72.

The operation of the overload circuit breaker as previously described isas follows:

If an excess current occurs when the circuit breaker is in its onposition, as illustrated in FIGURE 1, the bimetal strip 16 will beheated and will thereby bend toward the right of its position as shownin FIGURE 1 so as to press against the knob 29 of insulating materialand thereby to pivot the release lever 26 in a counterclockwisedirection. Arm 33 of pawl 32 then slides off the shoulder 31 on therelease lever 26 so that pawl 32 is released from its locked position.Spring 47 which presses against the arm 46 of control lever 45 thenmoves this lever upwardly from the position as shown in FIG- URE 1. Thepivot pin 44 of lever 45 thereby pivots the pawl 32 in the clockwisedirection about its axis 38 and lever 45 lifts the contact bridge 8 sothat its contacts 7 and 9 disengage from the fixed contacts 6 and 10 andthe circuit within the circuit breaker is interrupted. This movement ofcontrol lever 45 is supported by the cut-off spring 65 which maintainsthe surfaces 73 of the U- shaped carrier member 57 in engagement withthe pivot pin 44 when the switch mechanism is in the on positionaccording to FIGURE 1, and which becomes effective when pawl 32 isreleased by the release lever 26 sov that the carrier member 57 thenmoves the pivot pin 44 upwardly and pivots the pawl 32 in the clockwisedirection.

If a short-circuit current occurs, the magnet core 19 is energized andits extensions 22 and 23 then pull up the armature 24 and thereby pivotthe release lever 26 in the counterclockwise direction from the positionas shown in FIGURE 1 so that the circuit breaker will then be releasedin the manner as previously described. A trip-free release will occureven if the pushbutton 63 is held down or jammed in the depressedposition accord ing to FIGURE 1, since in this position there is noconnection between the pushbutton 63 and the control rod 62 or the partswhich are secured thereto, especially the carrier member 57, and thecontrol lever 45.

At each release of the circuit breaker the arm 46 of control lever 45 ispressed by spring 47 against an inclined surface 74 in the manner asshown in FIGURE 4. When the switch mechanism is in this off position,the notches 56 in the control lever 45 are in vertical alignment withthe projections 58 on the carrier member 57. Consequently, if thepushbutton 63 is then depressed, the projections 58 engage into thenotches 56 and thereby move the control lever 45 together with thecontact bridge 8 downwardly. However, the contacts 7 and 9 on thecontact bridge 8 will not as yet engage with the fixed contacts 6 andeven though the pushbutton 63 is depressed to its lowest possibleposition. During this downward movement of the control lever 45 itspivot pin 44 slides along the guide edges 42 of pawl 32 until it hitsagainst the noses 43 of the pawl and thereby pivots pawl 32 in thecounterclockwise direction about its axis 38 until the detents 41 ofpawl 32. slide over the pivot pin 44 of control lever 45. At the sametime, the release lever 26 is pivoted by the torsion spring 34 so thatits shoulder 31 engages with the arm 33 of pawl 32. If the operator ofthe circuit breaker then takes his finger off the pushbutton 63, theprojections 58 on the carrier member 57 disengage from the recesses 56in control lever 45 so that under the action of the compression spring47 this control lever will be pivoted with a rapid motion about itspivot pin 44 in the recesses 40 of pawl 32 and the contacts 7 and 9 ofcontact bridge 8 will be moved likewise with a rapid motion intoengagement with the fixed contacts 6 and 10. This engagement of thebridge contacts 7 and 9 with the fixed contacts 6 and 10 is so rapid asto be instantaneous. It occurs as soon as the projections 56' whichdefine the notches 56 slide off the projections 58 on the carrier member57.

When the circuit breaker is in the on position as illustrated in FIGURE1, the necessary contact pressure between the associated contacts 6, 7and 8, 9 is produced by the compression spring 47. In this on position,the notches 56 are located outside of the area of motion of theprojections 58 on the carrier member 57 so that an additional attempt todepress the pushbutton 63 cannot have any effect upon the on position ofcontact bridge 8 or upon the spring 47.

If the circut breaker according to the invention is to be switched offby hand, it is merely necessary to pull on the pushbutton 63 which isfor this purpose provided with a flange 63'. The upper laterallyprojecting surfaces 73 of the U-shaped carrier member 57 then engageupon the'pivot pin 44 of control lever 45. Since this pivot pin 44 is atthis time locked in a fixed position by pawl 32, the carrier member 57will be pivoted about the pivot pins 59 to the position as indicated inFIGURE 2. in dotand-clash lines. At this pivoting movement, a projection75 on the lower end of carrier member 57 hits against the armature 24and thereby pivots the release lever 26 in the counterclockwisedirection from the position as shown in FIGURE 1 so that the circuitbreaker is then released in the manner as previously described.

The overload circuit breaker according to the invention has very smallouter dimensions which are actually only one half of those as shown inthe drawings. It may be employed for rated currents up to 100 amp., andfor short-circuit currents at a direct voltage of 24 volts up to 10,000amp., and for low-voltage direct current circuits and medium-voltagealternating current circuits up to approximately 500' volts.

Although my invention has been illustrated and described with referenceto the preferred embodiment thereof, I wish to have it understood thatit is in no way limited to the details of such embodiment but is capableof numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. An overloadcircuit breaker comprising a housing, switch element provided withinsaid housing and including a control rod slidable longitudinally ofitself within said housing, a pushbutton secured to one end of saidcontrol rod and projecting from said housing for moving said circuitbreaker to the on position, a carrier member mounted on the other end ofsaid control rod, a pivotable control lever having a pivot pin,formations on said housing guiding said pivot pin for slidabledisplacement laterally of its axis, a contact bridge mounted on saidcontrol lever and movable from an oil": position to an on position andvice versa, a pawl pivotally mounted on said housing adjacent saidformations and engageable with said pivot pin of said control lever tolatch said pin in a fixed position when said contact bridge is in its onposition, a release lever pivotally mounted in said housing andreleasably engaging and maintaining said pawl in its latching position,excess current responsive means operable to pivot said release lever toits pawl releasing position, said control lever having a stop projectionthereon located outside the path of movement of said carrier member whensaid contact bridge is in its on position and located within said pathof move- -ment when said contact bridge is in its off position, a

pair of fixed contacts, and spring means acting upon said control leverand producing a constant contact pressure of said contact bridge againstsaid fixed contacts when said pivot pin is in said locked position andmoving said control lever, together with said contact bridge, to saidoff position when said pivot pin is released by said pawl.

2. An overload circuit breaker as defined in claim 1, in which saidhousing has an inclined surface, said control leverv being pressed bysaid spring means against said surface when said circuit breaker isswitched off, whereby said control lever is moved to a position in whichsaid stop projection is located within the path of movement of saidcarrier member.

3. An overload circuit breaker as defined in claim 1, in which said pairof fixed contacts are mounted in said housing at a right angle to eachother, said contact bridge being pivotably mounted on said control leverand having a substantially L-shape and being adapted to bridge said pairof fixed contacts.

4. An overload circuit breaker as defined in claim 3, further comprisinga one-armed lever pivotably mounted on said control lever and having afree end, and a second pivot pin, said contact bridge being pivotablymounted by said second pivot pin on said free end, the opposite walls ofsaid housing having corresponding grooves therein extending within thebisector of said right angle in which said fixed contacts are disposedrelative to each other, the two ends of said second pivot pin beingslidable and guided within said grooves.

5. An overload circuit breaker as defined in claim 4, in which saidcontact bridge is stamped so as to form a substantially L-shape centralpart and a lateral part on each side of said central part and partlyseparated therefrom by slots and bent in the opposite direction to saidcentral part so that all three parts together define a bearing hole,said second pivot pin extending through said bearing hole and throughcorresponding holes in said free end of said lever.

6. An overload circuit breaker as defined in claim 1, in which saidformations comprise slot means in said housing extending in thedirection of movement of said pushbutton and said control rod.

7. An Overload circuit breaker as defined in claim 5, in which said pawlhas a detent thereon adapted to engage with and to lock said pivot pinof said control lever, said pawl having a guide edge for said pivot pinof said control lever at one side of said detent and a nose projectingat the other side of detent adapted to engage with said pivot pin forpivoting said pawl to its locking position.

8. An overload circuit breaker as defined in claim 1, in which saidrelease lever has two arms, an electromagnet having a magnet core and anarmature for electromagnetically releasing the circuit breaker, one ofsaid arms of said release lever forming said armature, and a setscrewscrewed through the other arm, said setscrew having a head of insulatingmaterial, and a bimetal strip engageable with said head so as to pivotsaid release lever for effecting a thermal release of the circuitbreaker.

9. An overload circuit breaker as defined in claim 1,

in which said carrier member is pivotably mounted on said control rod, aspring acting upon said carrier member, said carrier member beingpivoted against the action of said last spring by said pivot pin of saidcontrol lever when locked by said pawl and when said pushbutton ismanually pulled outwardly of said housing, said carrier member, whenbeing thus pivoted, acting upon said release lever so as to pivot thesame and thereby to release the circuit breaker.

- 10. An overload circuit breaker as defined in claim 8, furthercomprising a connecting bar carrying one of said fixed contacts andhaving a part extending substantially parallel to said bimetal strip,said bimetal stripand said part of said connecting bar beinglongitudinally slotted and connected to each other so as to form atleast one coil winding, said magnet core extending through said slots.

11. An overload circuit breaker as defined in claim 6, furthercomprising a metal frame mounted in corresponding recesses in theopposite walls of said housing and containing said slots for guidingsaid pivot pin of said control lever, said pawl being pivotably mountedin said frame.

12. A pushbutton-actuated overload circuit breaker comprising a housing,a control rod slidable longitudinally of itself within said housing, apushbutton on the outer end of said control rod, a carrier mounted onthe inner end of said control rod, a pivotable switching lever having apivot pin, formations on said housing extending in the direction ofmovement of said control rod and said pushbutton and guiding said pivotpin for slidable displacement laterally of its axis, a contact bridgehaving an articulated connection to said switching lever at a point onthe latter spaced from its pivot axis, a pair of stationary contactsbridged by said contact bridge in the on position of said circuitbreaker, a pawl pivotally mounted on said housing adjacent saidformations and engageable with said pivot pin of said switching lever tolatch said pin in a fixed position when said contact bridge is in its onposition, a spring acting on said switching lever at a point thereonspaced from its pivot axis and maintaining the contact pressure betweensaid contact bridge and said stationary contacts, said spring, uponrelease of the pivot pin of said switching lever by said blocking pawl,biasing said switching lever, together with said contact bridge, to theoff position in which said contact bridge is disengaged from said switchcontacts, and an abutment in said housing, said switching lever beingpressed against said abutment by said spring in the off position of saidcontact bridge, said switching lever being formed with a recess which,in the oil position of said contact bridge, is in the range of movementof said carrier and, in the on position of said contact bridge, isoutside the range of movement of said carrier, said carrier, upon inwardmovement of said control rod, engaging in said recess to pivot andswitching lever toward the on position of said contact bridge, saidcarrier, upon release of said pushbutton, releasing said switching leverfor snap swinging to the on position, in which said contact bridgebridges said-fixed contacts, under the action of said spring, a releaselever pivotally mounted in said housing, said pawl, under the action ofsaid spring exerted through said switching lever upon said pawl,engaging said release lever and pivoting the same into a pawl latchingposition, and excess current-responsive means operable to pivot saidrelease lever to a position releasing said blocking pawl.

References Cited UNITED STATES PATENTS 2,895,028 7/1959 Ellenberger200-1 16 3,096,415 7/1963 Walters 200124 3,142,737 7/ 1964- Brackett200-116 BERNARD A. GILHIEANY, Primary Examiner. H. E. SPRINGBORN,Assistant Examiner.

1. AN OVERLOAD CIRCUIT BREAKER COMPRISING A HOUSING, SWITCH ELEMENTPROVIDED WITHIN SAID HOUSING AND INCLUDING A CONTROL ROD SLIDABLELONGITUDINALLY OF ITSELF WITHIN SAID HOUSING, A PUSHBUTTOM SECURED TOONE END OF SAID CONTROL ROD AND PROJECTING FROM SAID HOUSING FOR MOVINGSAID CIRCUIT BREAKER TO THE ON POSITION, A CARRIER MEMBER MOUNTED ON THEOTHER END OF SAID CONTROL ROD, A PIVOTABLE CONTROL LEVER HAVING A PIVOTPIN, FORMATIONS ON SAID HOUSING GUIDING SAID PIVOT PIN FOR SLIDABLEDISPLACEMENT LATERALLY OF ITS AXIS, A CONTACT BRIDGE MOUNTED ON SAIDCONTROL LEVER AND MOVABLE FROM AN OFF POSITION TO AN ON POSITION ANDVICE VERSA, A PAWL PIVOTALLY MOUNTED ON SAID HOUSING ADJACENT SAIDFORMATIONS AND ENGAGEABLE WITH SAID PIVOT PIN OF SAID CONTROL LEVER TOLATCH SAID PIN IN A FIXED POSITION WHEN SAID CONTACT BRIDGE IS IN ITS ONPOSITION, A RELEASE LEVER PIVOTALLY MOUNTED IN SAID HOUSING ANDRELEASABLY ENGAGING AND MAINTAINING SAID PAWL IN ITS LATCHING POSITION,EXCESS CURRENT RESPONSIVE MEANS OPERABLE TO PIVOT SAID RELEASE LEVER TOITS PAWL RELEASING POSITION, SAID CONTROL LEVER HAVING A STOP PROJECTIONTHEREON LOCATED OUTSIDE THE PATH OF MOVEMENT OF SAID CARRIER MEMBER WHENSAID CONTACT BRIDGE IS IN ITS ON POSITION AND LOCATED WITHIN SAID PATHOF MOVEMENT WHEN SAID CONTACT BRIDGE IS IN ITS OFF POSITION, A PAIR OFFIXED CONTACTS, AND SPRING MEANS ACTING UPON SAID CONTROL LEVER ANDPRODUCING A CONSTANT CONTACT PRESSURE OF SAID CONTACT BRIDGE AGAINSTSAID FIXED CONTACTS WHEN SAID PIVOT PIN IS IN SAID LOCKED POSITION ANDMOVING SAID CONTROL LEVER, TOGETHER WITH SAID CONTACT BRIDGE, TO SAIDOFF POSITION WHEN SAID PIVOT PIN IS RELEASED BY SAID PAWL.